The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having glass substrates uniformly and smoothly formed on its outer surface to increase the mechanical strength thereof and method of making the same.
As a display device of a television and a personal computer, etc., a large size cathode ray tube (CRT) display device has been used. However, since the screen must be separated from the electron gun more than predetermined distance for large size screen CRT, the volume is increased. Thus, this CRT cannot be applied to the thin weight, small size, and low power consumption electronic device such as a wall-mounted television, a portable television and a notebook computer, etc.
According to the purpose of display device, the flat panel display devices such as LCD (liquid crystal display), PDP (plasma display panel), ELD (electroluminescent display), and VFD (vacuum fluorescent display) have been introduced recently. Among above flat panel display device, the LCD has been dominantly researched for the good picture quality and low power consumption. The LCD-applied portable television and notebook computer are on the market resent, but there are also problems to be solved in this LCD yet. Particularly, the size and weight are important factor of the LCD investigation because of the apparatus have to be in hands of user.
For small size and light LCD, there are several methods of reducing the size and weight of the LCD element. However, the driving circuit and the thin film transistor, which are necessary element of the LCD, are so thin that the weight cannot be reduced. On the other hand, it is possible to reduce the weight of the glass substrate which is a basic element of the LCD. Specially, since the glass substrate is most heavy element of the LCD, the method of reducing the weight of the glass substrate has been continuously researched.
The light glass substrate means thin glass substrate. However, the thin glass substrate causes the damage and the surface roughness, so that the mechanical strength is weakened and the image quality of LCD is deteriorated.
In several etching methods of reducing the thickness of the glass substrate, it is representative that the substrate is etched in a case which was filled with etchant. In this etching method, however, because of impurities created in etching process, the substrate is not uniformly etched.
Therefore in proposed another etching method, the substrate is etched removing the impurities created in etching process by bubbles through a porous plate after a substrate is arranged.
In this method, however, bubbles appear on the substrate, or cracks occur by mechanical impulse, the bubbles were created in process of manufacturing glass and diameters of several um-several ten um. In case that the substrate applied to a LCD desirable image quality can not be achieved because of scattering of the light in a bubble region. Further if the cracks occur on the substrate by an etching process of the glass or mechanical impulse, impurities pass into the substrate in manufacturing process of the LCD thereby a quality of the LCD is down. In addition, since the crack is intensified according to passing of time, thereby the substrate is brokendown.
Accordingly in order to decrease weight of the LCD by etching the substrate, it is very important to decrease a fault on the substrate as well as an etching method.